Method of rifling gun barrels



Oct. 5, 1943. o. w. BoNNAFE 2,330,863

Y METHOD OF RIFLING GUN BARRELS Filed July 21, 1941 2 Sheets-Sheet l l l l l Oct. 5, 1943. v o. w. BONNAFE 2,330,353

' METHOD oF RIFLING GUN BARRELS Filed July 21, 1941 2 Sheets-Sheet 2 21 20 v 12 Feamin Cz/ensg i Ik .1457 1.494.5 I

I Paao 24 25 l 35 M, A

Patented Oct. 5, 1943 2,330,863 METHOD F RIFLING GUN BARRELS Oliver W. Bonnafe, Hudson, Mass., assigner to The Lapointe.' Machine Tool Company, Hudson, Mass., a corporation of Maine Application.Tilly 21, 1941,v Serial No.403,414

3 Claims.

This invention relates to the riing of gun barrels to provide a twist or spin'for the projectile. For this purpose, a plurality of shallow helical groves are formed in the bore of the gun.

it is the general object of my inventiontoj provide a more rapid and more economical meth-VA od of producing such helical grooves. More specically, I provide a method 'of riiiing gun barrels by a series of reaming andbroaching operations, which operations develop all of. the helical grooves simultaneously, rather than singly as heretofore practiced.

My invention further relates to certain or-y dered procedure which will behereinafter de-v scribed and more particularly pointed out in the 'appended claims.

Reamers and breaches 'adapted for use in theV practice of my improved method are shown in the drawings, in which w .A

Fig. -1 is a partial side elevation' of a broaching reamer adapted to perform the first reaming operation in my improved method; y

Figs. 2, 3, 4 and 5 are sectional end elevations,

taken along the lines 2 2, 3 3, 4 4 and 5 5' respectively in Fig. I;

Fig. 6 is a partial side elevation of the first grooving broach, adapted for performingthe initial notching and first grooving operations;

Figs. 7, 8, 9, and 11 are sectional end elevations, taken along the lines 7 1, 8 8, 9 5, IES-i9 and H l! in Fig. 6 respectively;

Fig. 12 is a partial side elevation of the second grooving breach, adaptedy iorperforming the second grooving operation;v A

Figs. 13,714, 15 and 16 are sectional end ele-- vations, taken along the lines-l3 l3, V[Il l, I5-l5 and I-IS in Fig. 12 respectively;

Fig. 17 is a partial side elevation of a broaching reamer, adapted for performingthe -second reaming operation; f l

Figs. 18, 19, 20 and 21 are sectional end elevations, taken" along the vlines kI8 Ii'}, {9 I9, 23-20, and 2| 2l in Fig.. 17 respectively;

Fig. 22 'is a partial side elevation ofthe sixth grooving breach, adapted forr performing the unal sizing and iinishing operation on the helical grooves produced by :the ,preceding operations;r

Figs. 23, 24, 25 and 26 are sectional yend elevations, taken along the lines 23 23, M Zf'i, 25 25 and 26--28 in Fig. 22 respectively;

Fig. 27 is a transverse sectional view Aof a gun barrel to be grooved or riiied;

Fig. 28 is a transverse sectionalI view of thev same barrel after ithas been rifled by my imy proved method; and

. of the gun barrel B which is to be groovediorA Fig. 29 is a conventionalized transverse `sec' tional view on an enlarged scale, showing the portionsV of stock removed successively by the tools shown in Figs. 1 to 26 inclusive.

By my improved method, I produce a completely rifled and reamed gun barrelk by passing a number of broaches once only through thebari rel to be riiled. Each of thesebroaches operatesv simultaneously on all of the grooves to be formed in the barrel. The rifling operation vis thusperformed much more expeditiously. thanv by the usual :procedure of forming each rifle groove separately and by repeatedly passing av singletooth cutter through each groove.

In Fig. 27 I have shown a transverse section rifled,and for purposes of illustrationhave indicated that the barrelw has an initial internal diameter. of 1.447. t

In Fig. 28 I have shown a transverse section of the same barrel B, after thebarrel-has been reamed and riied by my improved method. The reamed internaldiameter is now 1.457" and 'the barrel has been'provided with twelve grooves' G which are equally spaced and which have` an outside diameter of 1.497 at the bottoms oi'op-' posite grooves. f v

I will rst describe my generalmethod of operation, and I will then' describe the different broaches and their component parts in more? detail.

The general method of operation'willabe readily Aunderstood by reference to Fig. 29, :which isv an enlarged cross section of a segmental portion ofl a gun barrel, with a groove formedtherein .by my improved method. Fig. 29 hasbeenfcon-l ventionalized by showing the cuttingsection's as linear instead of curved, as the curvature would be very slight when the groove iseniarged 'tothe scale shown.

The une an in Fig. 29 represents the ini-nai in! ternal diameter of the gun barrel. B tov vbe broached. The section a represents the portion of stockjremoved by the operation of theiirstf broaching reamer (Fig. l) and the line Si repre sents the reamed surface.

The stock removed by the rst groovingbroach. The portion b., which is re1atively narrow, is removed. to` fullf (-Fig. 6) is indicated at b and b'.

depth by a single notching cutter and the .spaced portions b are removed by a plurality of successively-operatng broaching cutters, `all as shown in Fig. 6. The line 32 indicates-the depth of the rst grooving cut.

- The letters c, d, e and f (Fig. 29') indicatey ne ing in the specification will show that the first pilot in the sixth grooving breach has the same outside diameter as the rear pilot of the fifth grooving breach, also that the tooth width has been substantially increased from .200" to .2334 but that the over-all diameter of the rst cutter has been reduced to 1.461", as compared with a diameter of 1.496" for the last cutter which previously7 operated. f

The sixth grooving breach thus cuts rst at the edges of the grooves only, but increases in depth of cut more rapidly than with the preceding breaches, the increase in diameter being preferably around .003" per cutter.

The nal grooving cutter (or cutters) 82 has an outside diameter of 1.497, as compared with 1.496" for the last grooving cutter of the fth breach, showing that the final cutter not only reams the sides of each groove to full width but also takes a inal thin iinish cut over the bottoms of the grooves.

The tooth section in the final cutters of the sixth grooving breach is also slightly modified to leave rounded fillets at the inner and outer corners ef the grooves, as shown at 31 and 38 in Fig. 29.

The function and operation of the different breaches will be readily apparent from the foregoing description, taken with the diagram in Fig. 29 which clearly indicates the portions of stock removed by each reamer or breach in the successive steps of my improved riiiing method.

The following table shows the comparative dimensions of the two reamers and siX breaches used in the method of rifling gun barrels above described.

It will be understood that the dimensions given in this table (and also as shown in the drawings) are illustrative only, and that these dimensions,l

as well as the number of breaches and the number of cutters per breach, may all be varied to suit operating conditions. The number of riiie grooves in the gun barrel may also be increased or decreased.

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but what I claim is:

l. The method of riing gun barrels which comprises initially reaming the bore of said barrel, breaching a plurality of initial helical grooves in said barrel, increasing the depth and slightly decreasing the width of said grooves by successive helical breaching operations, each performed on all of said grooves simultaneously, reaming and thereby finishing the bore of said barrel, and thereafter increasing the width and progressively increasing the depth of said grooves to finish' width and depth by a iinal helical breaching operation.

2. The method of riing gun barrels which comprises breaching a plurality of initial helical grooves in said barrel, increasing the depth and slightly decreasing the Width of said grooves by successive helical breaching operations, each performed on all of said grooves simultaneously and each removing `approximately equal increments of material from said grooves, reaming land thereby finishing the bore of said barrel, and

,finishing the rifle grooves by passing an additional finish breach therethrough in a helical path which additional breach progressively increases said grooves to full width and depth. 

